Semiconductor devices are commonly found in modern electronic products. Semiconductor devices vary in the number and density of electrical components. Discrete semiconductor devices generally contain one type of electrical component, e.g., light emitting diode (LED), small signal transistor, resistor, capacitor, inductor, and power metal-oxide-semiconductor field-effect transistor (MOSFET). Integrated semiconductor devices commonly contain hundreds to millions of electrical components. Examples of integrated semiconductor devices include microcontrollers, microprocessors, charged-coupled devices (CCDs), solar cells, and digital micro-mirror devices (DMDs).
Semiconductor devices perform a wide range of functions such as signal processing, high-speed calculations, transmitting and receiving electromagnetic signals, controlling electronic devices, transforming sunlight to electricity, and creating visual projections for television displays. Semiconductor devices are found in the fields of entertainment, communications, power conversion, networks, computers, and consumer products. Semiconductor devices are also found in military applications, aviation, automotive, industrial controllers, and office equipment. In particular, power MOSFETs are commonly used in electronic circuits, such as communication systems and power supplies, as electric switches to enable and disable the conduction of relatively large currents in, e.g., DC-to-DC voltage converters, power supplies, and motor controllers.
A power MOSFET device includes a large number of MOSFET cells or individual transistors that are connected in parallel and distributed across a surface of a semiconductor die. Power MOSFET devices are typically used as electronic switches to control power flow to a circuit. A control signal at a gate terminal of the power MOSFET controls whether current flows through the MOSFET between a drain terminal and source terminal of the MOSFET. The conduction path between the drain terminal and source terminal of a MOSFET is wired in series with a circuit to be switched, so that when the MOSFET is off, i.e., the MOSFET limits electric current between the source and drain terminals, current is limited through the switched circuit. When the MOSFET is on, electric current flows through both the MOSFET and the switched circuit, in series, to power the switched circuit.
One consideration in the design and manufacture of a power MOSFET is the electrical resistances between doped regions in a MOSFET and the external package contacts presented to an engineer designing a circuit including the power MOSFET. Reducing electrical resistance in metal layers formed on a MOSFET, as well as redistribution layers (RDL) and leadframe of the MOSFET package, reduces the amount of wasted power dissipated into the MOSFET during use.